There is an electrostatic levitation furnace as a conventional levitation furnace, which is provided with a flat and nearly cylindrical shaped vacuum chamber, a pair of main electrodes disposed on Z-axis that is an axis of this vacuum chamber, a pair of auxiliary electrodes respectively disposed on X-axis and Y-axis intersecting perpendicularly to the Z-axis, and a plurality of access ports disposed two-dimensionally in a periphery of the vacuum chamber at predetermined spaces. The respective access ports are equipped with various apparatuses, such as a laser irradiator for heating the sample, a position detector for the sample, a thermal measuring device for the sample, an illuminator, a camera and so on.
In the electrostatic levitation furnace described above, the sample charged between main electrodes is charged by electrode contact, ultraviolet irradiation or heating, and made in the levitation state by the electrostatic field generated between main electrodes. In this time, the sample is held in the predetermined position by controlling electric potential between main electrodes and between auxiliary electrodes, and the sample is heated and molten by irradiating laser beams thereon. It is possible to generate a crystal without external interference by cooling and solidifying the sample heated and molten in this manner.
Additionally, although there is a furnace designed so as to levitate the sample by using an acoustic wave or an electromagnetic method as the furnace for making the sample in the levitation state, it is necessary to introduce a gaseous body into the furnace in a case of using the acoustic wave, so that the sample may be influenced by the gaseous body, and the sample is confined to a conductive body in a case of using the electromagnetic method. As compared with above, the electrostatic levitation furnace has the advantage in that the furnace can be applied also to the sample other than the magnetic body without the influence of the gaseous body because of making the inside of the furnace vacuous.
However, in the aforementioned conventional electrostatic levitation furnace, the main electrodes is disposed on the axis of the vacuum chamber and the access ports is disposed two-dimensionally along the outer periphery of the vacuum chamber, therefore there are problems as follow.
{circle around (1)} It is difficult to increase the number of the apparatuses for access and distribute these apparatuses since the accessible direction against the sample is substantially limited within only one plane and the auxiliary electrodes are also disposed on this plane.
{circle around (2)} The auxiliary electrodes of which electrostatic field intensity is low as compared with the main electrodes cannot but be used for reasons of distributing the various apparatuses, so that controlling forces in the directions of X and Y-axes becomes weak.
{circle around (3)} If the access ports are increased in number according to demand of access against the sample, the outer diameter of the vacuum chamber becomes larger and the equipment becomes larger in the whole body because the vacuum system becomes necessary to increase the capacity following this. In a case of scaling up of the equipment in the whole body as mentioned above, the distance from the sample becomes longer, so that the access against the sample becomes difficult, furthermore it becomes improper to be used in the spacecraft in which there is a severe limitation in size and weight.
{circle around (4)} It is difficult to heat the sample uniformly because the irradiating direction of laser beams is also restricted within one plane.
Further, there is also a problem in that the respective electrodes are fixed to the vacuum chamber in the conventional electrostatic levitation furnace and it is not possible to change the space between the electrodes and the size of the electrodes according to size of the sample or so.